<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
</head>

<body>
    <div id="root">
        <button @click="count++">累加器</button>
        <p>内容:{{count}}</p>
    </div>
    <script>
        Vue.config.productionTip = false;	 // 阻止 Vue在启动时生成生产提示
        
        const vm = new Vue({
            el: "#root", // 挂载的容器
            data() { // 数据
                return {
                    count:0
                }
            },
            methods: {
                unWatch: () => {},
            },
        })
        vm.unWatch = vm.$watch(
            'count',function () {
                console.log('count改变了');
                console.log(this);
            },{
                deep:true,  // 深度监听
                immediate:true,  // 立即监听
            }
        )
</script>
</body>

</html>